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Article

Khawaja Shafiq Haider, Aamina Bintul Huda, Akhtar Rasool and Syed Hashim Raza Bukhari

The purpose of this paper is to identify the fault modes of a nonlinear twin-rotor system (TRS) using the subspace technique to facilitate fault identification, diagnosis…

Abstract

Purpose

The purpose of this paper is to identify the fault modes of a nonlinear twin-rotor system (TRS) using the subspace technique to facilitate fault identification, diagnosis and control applications.

Design/methodology/approach

For identification of fault modes, three types of system malfunctions are introduced. First malfunction resembles actuator, second internal system dynamics and third represents sensor malfunction or offset. For each fault scenario, the resulting TRS model is applied with persistently exciting inputs and corresponding outputs are recorded. The collected input–output data are invoked in NS4SID subspace system identification algorithm to obtain the unknown fault model. The identified actuator fault modes of the TRS can be used for fault diagnostics, fault isolation or fault correction applications.

Findings

The identified models obtained through system identification are validated for correctness by comparing the response of the actual model under the fault condition and identified model. The results certify that the identified fault modes correctly resemble the respective fault conditions in the actual system.

Originality/value

The utilization of proposed work for current research emphasized the area of fault detection, diagnosis and correction applications that makes its value significantly. These modes when used for diagnosis purposes allow users to timely get intimated and rectify the performance degradation of the plant before it gets totally malfunctioned. Moreover, the slight performance degradation is also indicated when fault diagnosis is performed.

Details

International Journal of Intelligent Unmanned Systems, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2049-6427

Keywords

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Article

Akhtar Rasool, Esref Emre Ozsoy, Fiaz Ahmad, Asif Sabanoviç and Sanjeevikumar Padmanaban

This paper aims to propose a novel grid current control strategy for grid-connected voltage source converters (VSCs) under unbalanced grid voltage conditions.

Abstract

Purpose

This paper aims to propose a novel grid current control strategy for grid-connected voltage source converters (VSCs) under unbalanced grid voltage conditions.

Design/methodology/approach

A grid voltage dynamic model is represented in symmetrical positive and negative sequence reference frames. A proportional controller structure with a first-order low-pass filter disturbance observer (DOB) is designed for power control in unbalanced voltage conditions. This controller is capable of meeting the positive sequence power requirements, and it also eliminates negative sequence power components which cause double-frequency oscillations on power. The symmetrical components are calculated by using the second-order generalized integrator-based observer, which accurately estimates the symmetrical components.

Findings

Proportional current controllers are sufficient in this study in a wide range of operating conditions, as DOB accurately estimates and feed-forwards nonlinear terms which may be deteriorated by physical and operating conditions. This is the first reported scheme which estimates the VSC disturbances in terms of symmetrical component decomposition and the DOB concept.

Originality/value

The proposed method does not require any grid parameter to be known, as it estimates nonlinear terms with a first-order low-pass filter DOB. The proposed control system is implemented on a dSPACE ds1103 digital controller by using a three-phase, three-wire VSC.

Details

World Journal of Engineering, vol. 14 no. 6
Type: Research Article
ISSN: 1708-5284

Keywords

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Article

Fiaz Ahmad, Akhtar Rasool, Esref Emre Ozsoy, Asif Sabanoviç and Meltem Elitas

This paper aims to propose a robust cascaded controller based on proportional-integral (PI) and continuous sliding mode control.

Abstract

Purpose

This paper aims to propose a robust cascaded controller based on proportional-integral (PI) and continuous sliding mode control.

Design/methodology/approach

Cascaded control structure is an attractive control scheme for DC-DC power converters. It has a two-loop structure where the outer loop contains PI controller and the inner loop uses sliding mode control (SMC). This structure thus combines the merits of both the control schemes. However, there are some issues that have prohibited its adoption in industry, the discontinuous nature of SMC which leads to variable switching frequency operation and is hard to realize practically. This paper attempts to overcome this issue by changing the discontinuous functionality of SMC to continuous by utilizing the concept of equivalent control.

Findings

The robustness of the controller designed is verified by considering various cases, namely, ideal case with no uncertainties, sudden variation of input supply voltage, load resistance, reference voltage, circuit-parameters and for noise disturbance. The controller effectiveness is validated by simulating the DC-DC boost and Cuk converters in SimPowerSystems toolbox of MATLAB/Simulink. It is shown that the performance of the proposed controller is satisfactory, and both reference output voltage and inductor current are tracked with little or no sensitivity to disturbances.

Originality/value

The results for various scenarios are interesting and show that the controller works quite satisfactorily for all the simulated uncertainties.

Details

World Journal of Engineering, vol. 14 no. 5
Type: Research Article
ISSN: 1708-5284

Keywords

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Article

Fiaz Ahmad, Kabir Muhammad Abdul Rashid, Akhtar Rasool, Esref Emre Ozsoy, Asif Sabanoviç and Meltem Elitas

To propose an improved algorithm for the state estimation of distribution networks based on the unscented Kalman filter (IUKF). The performance comparison of unscented…

Abstract

Purpose

To propose an improved algorithm for the state estimation of distribution networks based on the unscented Kalman filter (IUKF). The performance comparison of unscented Kalman filter (UKF) and newly developed algorithm, termed Improved unscented Kalman Filter (IUKF) for IEEE-30, 33 and 69-bus radial distribution networks for load variations and bad data for two measurement noise scenarios, i.e. 30 and 50 per cent are shown.

Design/methodology/approach

State estimation (SE) plays an instrumental role in realizing smart grid features like distribution automation (DA), enhanced distribution generation (DG) penetration and demand response (DR). Implementation of DA requires robust, accurate and computationally efficient dynamic SE techniques that can capture the fast changing dynamics of distribution systems more effectively. In this paper, the UKF is improved by changing the way the state covariance matrix is calculated, to enhance its robustness and accuracy under noisy measurement conditions. UKF and proposed IUKF are compared under the cummulative effect of load variations and bad data based on various statistical metrics such as Maximum Absolute Deviation (MAD), Maximum Absolute Per cent Error (MAPE), Root Mean Square Error (RMSE) and Overall Performance Index (J) for three radial distribution networks. All the simulations are performed in MATLAB 2014b environment running on an hp core i5 laptop with 4GB memory and 2.6 GHz processor.

Findings

An Improved Unscented Kalman Filter Algorithm (IUKF) is developed for distribution network state estimation. The developed IUKF is used to predict network states (voltage magnitude and angle at all buses) and measurements (source voltage magnitude, line power flows and bus injections) in the presence of load variations and bad data. The statistical performance of the coventional UKF and the proposed IUKF is carried out for a variety of simulation scenarios for IEEE-30, 33 and 69 bus radial distribution systems. The IUKF demonstrated superiority in terms of: RMSE; MAD; MAPE; and overall performance index J for two measurement noise scenarios (30 and 50 per cent). Moreover, it is shown that for a measurement noise of 50 per cent and above, UKF fails while IUKF performs.

Originality/value

UKF shows degraded performance under high measurement noise and fails in some cases. The proposed IUKF is shown to outperform the UKF in all the simulated scenarios. Moreover, this work is novel and has justified improvement in the robustness of the conventional UKF algorithm.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

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Article

Fiaz Ahmad, Akhtar Rasool, Esref Emre Ozsoy, Asif Sabanoviç and Meltem Elitas

The purpose of this paper is to propose successive-over-relaxation (SOR) based recursive Bayesian approach (RBA) for the configuration identification of a Power System…

Abstract

Purpose

The purpose of this paper is to propose successive-over-relaxation (SOR) based recursive Bayesian approach (RBA) for the configuration identification of a Power System. Moreover, to present a comparison between the proposed method and existing RBA approaches regarding convergence speed and robustness.

Design/methodology/approach

Swift power network configuration identification is important for adopting the smart grid features like power system automation. In this work, a new SOR-based numerical approach is adopted to increase the convergence speed of the existing RBA algorithm and at the same time maintaining robustness against noise. Existing RBA and SOR-RBA are tested on IEEE 6 bus, IEEE 14 bus networks and 48 bus Danish Medium Voltage distribution network in the MATLAB R2014b environment and a comparative analysis is presented.

Findings

The comparison of existing RBA and proposed SOR-RBA is performed, which reveals that the latter has good convergence speed compared to the former RBA algorithms. Moreover, it is robust against bad data and noise.

Originality value

Existing RBA techniques have slow convergence and are also prone to measurement noise. Their convergence speed is effected by noisy measurements. In this paper, an attempt has been made to enhance convergence speed of the new identification algorithm while keeping its numerical stability and robustness during noisy measurement conditions. This work is novel and has drastic improvement in the convergence speed and robustness of the former RBA algorithms.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Muhammad Ramzan Akhtar

The Prophet Muhammad (pbuh) laid the foundations of the Islamic state in Medina in 622 A.D. The state expanded gradually during the 10‐year rule of the Prophet (pbuh). The…

Abstract

The Prophet Muhammad (pbuh) laid the foundations of the Islamic state in Medina in 622 A.D. The state expanded gradually during the 10‐year rule of the Prophet (pbuh). The Arabian Peninsula and Southern Palestine were conquered during that period. The state expanded enormously during the reign of Umar (RA). Many countries of the Roman and Persian empires comprising an area of more than 2.2 million were annexed. Historians have noted that this framework played a vital role in integrating these people which in turn strengthened the state.

Details

Humanomics, vol. 14 no. 4
Type: Research Article
ISSN: 0828-8666

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Article

Umar Iqbal Siddiqi, Jin Sun and Naeem Akhtar

The study aims to examine the effects of ulterior motives in peer and expert supplementary online hotel reviews on consumers' perceived deception, dissatisfaction, and its…

Abstract

Purpose

The study aims to examine the effects of ulterior motives in peer and expert supplementary online hotel reviews on consumers' perceived deception, dissatisfaction, and its downstream effects on altruistic response and repurchase intentions. The research also examines the moderating role of hotel attribute performance on perceived deception and its consequents.

Design/methodology/approach

This study used convenient non-probability sampling and collected data from 448 inbound tourists in China. It used partial least square structural equation modeling technique and SmartPLS 3.0 for analyzing the main and moderating effects of the variables.

Findings

The ulterior motives in peer and expert supplementary reviews significantly affect perceived deception, further leading to consumers' dissatisfaction and engagement in altruistic response. Noticeably, consumers' dissatisfaction is positively associated with repeat purchase intentions. Hotel attribute performance significantly moderates the relationship between the ulterior motives in supplementary reviews and consumers' perceived deception.

Originality/value

The study examines the key issue in online hotel reviews using the expectancy disconfirmation theory and identifies consumers' altruistic behavior because of their dissatisfaction, contributing to ethics and consumer behavior literature. Moreover, the research offers prolific implications for hotel and travel websites and hoteliers in the study context.

Details

Asia Pacific Journal of Marketing and Logistics, vol. 33 no. 1
Type: Research Article
ISSN: 1355-5855

Keywords

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Expert briefing

Peace talks prospects.

Details

DOI: 10.1108/OXAN-DB210234

ISSN: 2633-304X

Keywords

Geographic
Topical
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Expert briefing

The militants' losses demonstrate their resilience rather than weakness. Kabul is trying to restart talks with the Taliban and assert ownership of the process. Whether the…

Details

DOI: 10.1108/OXAN-DB221907

ISSN: 2633-304X

Keywords

Geographic
Topical
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Executive summary

AFGHANISTAN: Taliban strength is bad news for IS

Details

DOI: 10.1108/OXAN-ES216633

ISSN: 2633-304X

Keywords

Geographic
Topical
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